A multiple-input multiple-output (MIMO) technology, that is, a multiple-antenna technology, is widely used in a Long Term Evolution (LTE) system. Affected by factors such as the atmosphere and plants, in some cases, wireless transmission has a very large path loss. A precoding technology in multiple antennas can compensate for the loss to an extent.
To compensate for path losses of a common channel and a traffic channel, a terminal device may feed back channel state information (CSI) of the common channel and CSI of the traffic channel to a base station. The base station performs precoding on sent data by using the fed-back CSI. However, in the prior art, when the terminal device feeds back the CSI of the common channel and the CSI of the traffic channel, overheads required for feeding back the CSI are relatively large, wasting a system resource.